* 1. Remove PYTHON_FLAGS from paddle_build.sh in paddlepaddle/paddle:latest-dev
* 1. Add PYTHON_FLAGS back
2. Change SIGKILL to SIGINT and SIGTERM
* 1. Add setup.py.in back
* 1. add pip install open-cv in Dockerfile to avoid libusb_exit hanging up which is caused by the opencv-python package missing
* 1. Add the && \ to line above
* 1. Remove the notice comment